It is known in the prior art to utilize a chopper for regulating the current in the propulsion motor circuit of a transit vehicle moving along a roadway track as described in an article published in the Westinghouse Engineer for March 1973 at pages 34 to 41. A conduction control apparatus responsive to an effort request P signal determines the ON conduction of the main thyristor switch within the chopper. A commutation circuit is provided to turn OFF the main thyristor switch of the chopper, which commutation circuit includes a turn-off thyristor and a charge storage capacitor charged to the same voltage level as the line voltage source. Propulsion motors have been controlled by a software program controlled microprocessor as disclosed in U.S. Pat. Nos. 4,090,115 of J. H. Franz, 4,095,153 of T. C. Matty and J. H. Franz, and 4,123,693 of L. W. Anderson and J. H. Franz.
In an article entitled "Propulsion Control for Passenger Trains Provides High Speed Service" that was published in the Westinghouse Engineer for September 1970 at pages 143 to 149 there is discussed the operation of the P signal to establish the requested tractive effort of the vehicle.